One Prop Per State: Rethinking React's Controlled/Uncontrolled Boilerplate

If you've ever wrapped a <Select>, <DatePicker>, or <Dialog>, you've written this: function Select({ value, defaultValue, onChange }) { const [internal, setInternal] = useState(defaultValue); const isControlled = value !== undefined; // runtime mode check const current = isControlled ? value : internal; // two sources of truth...